The example starts as so,
a crate has a square base of width (and length) x metres and is of height h metres. The haulage company will only transport crates provided that the sum of the length, width and height of a crate is not more than 5 metres. The firm wishes to maximise the volume V of the crate.
I want to explain why h = 5 - 2X if we want to maximise V,
and also to show that the quantity to be maximised is V = 5X^2 - 2X^3
not really sure ive got a grip on this one any help appreciated